Self-drilling rock anchor

ABSTRACT

A self-drilling rock anchor includes a drilling head ( 16; 46 ) provided at one end ( 13 ) of the receiving body ( 12 ), an inner tube ( 21 ) for receiving a pressurable-out hardenable mass ( 26 ) and provided in the receiving body ( 12 ) and having an outlet opening ( 22 ) spaced from the drilling head ( 16; 46 ), and a mixing member ( 31; 61 ) displaceably supported in the inner tube ( 21 ), with the drilling head ( 16; 46 ) having a receptacle ( 18; 48 ) adjacent to the mixing member ( 31; 61 ) for receiving a free end ( 32; 62 ) of the mixing member ( 21; 61 ) and a through-opening ( 17 ) for the hardenable mass ( 26 ), and the receptacle ( 18; 48 ) of the drilling head ( 16; 46 ) having a centering section ( 20; 50 ) that cooperates with a counter-centering section ( 33; 63 ) provided at the free end ( 32; 62 ) of the mixing member ( 31; 61 ) adjacent to the drilling head ( 16; 46 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a self-drilling rock anchor including ahollow cylindrical receiving body, a drilling head provided at one endof the receiving body, an inner tube for receiving a pressurable-outhardenable mass and provided in the receiving body and having an outletopening spaced from the drilling head, a mixing member displaceablysupported in the inlet tube, with the drilling head having a receptacleadjacent to the mixing member for receiving a free end of the mixingmember and a through-opening for the hardenable mass.

2. Description of the Prior Art

Rock anchors are attachment elements which are used for stabilization ofwalls of hollow spaces such as tunnels, galleries, and the like and, inparticular, for connecting rock regions adjacent to a wall with eachother. In many cases, the regions which are located immediately adjacentto the wall and mechanical characteristics of which, in particular theload-carrying capacity, are reduced as a result of formation of hollowspaces, are connected to more remote, undamaged regions. The wall, inthis regard, means the ceiling and side walls of a hollow space and alsoits bottom.

German Publication DE 103 01 968 A1 discloses a self-drilling rockanchor provided at the working tool side with a pressable-out mortarmass. The rock anchor is drilled in a constructional component. In theintermediate space between the inner tube and the receiving member andin the free space between the outlet opening of the inner space and thedrilling head, at a dry drilling process, particles, which arecommutated by the drilling head, so-called drillings, are aspirated.Alternatively, at a wet drilling process, rinsing water is fed to thedrilling head through the intermediate space and the free space. Inorder to provide a sufficient intermediate space, spacers are providedon the inner tube. The spacers are separate elements or are formedduring manufacturing of the inner tube. Upon reaching a desired settingdepth, the mortar mass, which is located in the inner tube, e.g., ispacked in a film bag, is squeezed out under pressure, with a mixingelement which is located in front of the pressable-out mass, beingdisplaceable in a receptacle of the drilling head. The squeezable-outmortar mass, e.g., a multicomponent mortar mass, upon furtherapplication of pressure, is mixed in the mixing element and is squeezedthrough the through-opening of the drilling head into the space thatsurrounds the rock anchor.

Because of the initially displaced mixing element, no hardenable masspenetrates in the intermediate space between the receiving member andthe inner tube. In this way, the need in an expensive hardenable mass islimited to the amount necessary to fill the space between the outer bodyand the bore wall. After hardening of the mortar mass, the rock anchoris chemically anchored in the constructional component.

Dependent on the type of the constructional component, a plurality ofrock anchors must be used for stabilization of walls of hollow spaces.Therefore, there is further a need, with such, rock anchors, to reducetheir manufacturing costs.

Accordingly, an object of the present invention is to provide a rockanchor that can be economically produced in comparison with the knownrock anchors.

Another object of the present invention is to provide a rock anchor thatwould insure pressing out of the pressable-out of the pressable-out massinto the space that surrounds the receiving member, almost without anyloss of the hardenable mass.

SUMMARY OF THE INVENTION

These and other objects of the present invention, which will becomeapparent hereinafter, are achieved by providing a rock anchor of thetype discussed above in which the receptacle of the drilling head has acentering section that cooperates with a counter-centering sectionprovided at the free end of the mixing member adjacent to the drillinghead. In this way, the free end of the mixing member, which is locatedadjacent to the drilling head, as a result of the press-out process,upon being displaced, is automatically received in the drilling headreceptacle. This takes place without use of a separate spacer or anadditional guide member arranged in the receiving tube such as, e.g., aramp. When the free end of the mixing member impacts an edge of thedrilling head adjacent thereto, the mixing member, as a result of theshape of the free end thereof, upon continuation of the press-outprocess, is deflected in the receptacle of the drilling head. As soon asthe free end of the mixing member occupies a proper position in thecentering section of the receptacle of the drilling head, the mixedhardenable mass can flow through the through-opening in the drillinghead and fill the space that surrounds the receiving body.

Advantageously, the mixing member is formed of a plastic material andhas, in particular, in the region of the counter-centering section ofthe free end of the mixing member, elastic deformation characteristics.Advantageously, the free end of the mixing member is provided, in theregion of the counter-centering section, with slots extending parallelto the longitudinal axis of the inner tube. The slots advantageouslyinsure elastic deformation characteristics of the counter-centeringsection upon joint displacement with the centering section of thereceptacle of the drilling head.

During a drilling process, the inner tube, together with thepressable-out mass, can wobble, so that an adequate intermediate spacebetween the inner tube and the receiving body for aspirating drillingsor drilling dust or for feeding of rinsing water to the drilling head isinsured.

The manufacturing costs of the inventive rock anchor in comparison withthe known rock anchor are reduced, which is an important advantage ofsuch a mass-produced element. Despite this, a perfect use of theself-drilling rock anchor is insured.

Advantageously, the centering section of the receptacle of the drillinghead has a funnel shape and tapers toward the free end of the drillinghead. This shape of the centering section facilitates joint displacementwith the free conical end of the mixing member tapering in a directionof the drilling head.

Advantageously, a wall section of the centering section that surroundsthe receptacle of the drilling head is formed concave. Thereby, duringthe displacement of the mixing member, an advantageous deflection of thefree end of the mixing member in the receptacle of the drilling head isinsured. In this connection, the term “concave” relates to the shape ofthe corresponding wall section. According to an advantageous embodiment,the wall section that surrounds the receiving space of the drilling headreceptacle, forms a partially spherical receptacle.

Advantageously, a wall section of the counter-centering section thatsurrounds the end region of the free end of the mixing member is formedconvex. Thereby, upon displacement of the mixing member, an advantageousdeflection of the free end of the mixing member in the drilling headreceptacle is insured. In this connection, the term “convex” relates tothe shape of the corresponding wall section. According to anadvantageous embodiment the wall section that surrounds the end regionof the free end of the mixing member, forms a crowned or spherical shapeof the free end of the mixing member.

Advantageously, the centering section of the receptacle of the drillinghead has a diameter larger than a diameter of the counter-centeringsection of the free end of the mixing member. This insures that the freeend of the mixing member can be received in the receptacle of thedrilling head.

Advantageously, the counter-centering section is formed of severalcentering elements formed at the free end of the mixing member. Theplurality of centering elements provide for deflection of the free endof the mixing member in the receptacle of the drilling head. It isparticularly advantageous when the centering elements are arrangedrotationally symmetrically with respect to a longitudinal axis of theinner tube, e.g., along a double-or-multiple rotational axis. Thereby,the free end of the mixing element can be deflected in the drilling headreceptacle in each position of the inner tube.

Preferably, a stop for the mixing member is provided in the receptacleof the drilling head, which limits the displacement of the mixingmember. The stop is formed, e.g., as a circumferential rim provided inthe receptacle of the drilling head in the direction of the free end ofthe drilling head adjacent to the centering section. The stop wouldlimit the displacement of the mixing member during the press-outprocess. This insures that the end region of the free end of the mixingmember is not deformed, during its displacement, to an extent that thedischarge of the mixed, pressed-out mass is restricted.

The novel features of the present invention, which are considered ascharacteristic for the invention, are set forth in the appended claims.The invention itself, however, both as to its construction and its modeof operation, together with additional advantages and objects thereof,will be best understood from the following detailed description ofpreferred embodiments, when read with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 A longitudinal cross-sectional view of a first embodiment of arock anchor according to the present invention;

FIG. 2 a longitudinal cross-sectional view of a front portion of asecond embodiment of the rock anchor according to the present invention;and

FIG. 3 a view at the free end of the mixing member of the rock anchorshown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A self-drilling rock anchor 11, which is shown in FIG. 1, has a hollowcylindrical receiving body 12, a drilling head 16 provided at a first,facing in the setting direction S, end 13 of the receiving body 12, androtation application means 15, e.g., in form of a polygon connectablewith a rotary drilling tool, and which is provided at an opposite,second end 14 of the receiving body 12. The drilling head 16 has athrough-opening 17 and a receptacle 18 with a funnel-shaped centeringsection 20 tapering toward the free end of the drilling head 16.

In the receiving body 12, and inner tube 21 is arranged in which apressable-out and hardenable mass 26, which is packed in a foil bag, isarranged. The inner tube 21 has an outlet opening 22 spaced from thedrilling head 16. In the inner tube 21, between the hardenable mass 26and the drilling head 16, there is provided a displaceably supportedmixing member 31 in an end region of which at the free end 32 of themixing member 31, there is provided a counter-centering section 33 thatcooperates with the centering section 20 of the receptacle 18 of thedrilling head 16.

A wall section of the centering section 20 of the receptacle 18 of thedrilling head 16, which is adjacent to the mixing member 31, is formedconcave. In the receptacle 18 of the drilling head 16, there is provideda stop 19 for the mixing member 31. A wall section of thecounter-centering section 33, which surrounds the free end 32 of themixing member 31, is formed convex. The diameter D1 of the centralsection 20 of the receptacle 18 of the drilling head 16 is larger thanthe diameter d1 of the counter-centering section 33 of the end region ofthe free end 32 of the mixing member 31.

Upon reaching a desired bore depth, the pressable-out mass 26 is ejectedunder pressure. At that, firstly the mixing member 31 is displaced inthe direction of the drilling head 16 until the free end 32 of themixing member 31 lies in the receptacle 18 of the drilling head 16.

Upon application of pressure further to the pressable-out mass 26, it isejected through the opening 17 in the drilling head 16 and out of therock anchor 11.

A self-drilling rock anchor 41, which is shown partially in FIGS. 2-3,is formed identically to the rock anchor 11 up to the shape of thecentering section 50 of the receptacle 48 of the drilling head 46 andthe counter-centering section 63 of the free end 62 of the mixing member61, and identical parts are designated with the same reference numerals.

The wall sections that surround the centering section 50 are formedconcave and have a diameter D2. At the free end 62 of the mixing member61, there are provided several centering elements 64 which are arrangedrotationally symmetrically with respect to a longitudinal axis 23 of theinner tube 21. The free ends of the centering elements 64 are adjacentto each other. The wall sections which surround the counter-enteringsection 63 and which correspond to the radially outer surfaces of thecentering elements 64, form a convex or crowned shape of the end regionof the free end 62 of the mixing member 61. The diameter d2 of thecounter-centering section 63 is smaller than the diameter D2 of thecentering section 50.

Though the present invention was shown and described with references tothe preferred embodiments, such are merely illustrative of the presentinvention and are not to be construed as a limitation thereof andvarious modifications of the present invention will be apparent to thoseskilled in the not intended that the present invention be limited to thedisclosed embodiments or details thereof, and the present inventionincludes all variations and/or alternative embodiments within the spiritand scope of the present invention as defined by the appended claims.

1. A self-drilling rock anchor (11; 41), comprising: a hollowcylindrical receiving body (12); a drilling head (16; 46) provided atone end (13) of the receiving body (12); an inner tube (21) forreceiving a pressurable-out hardenable mass (26) and provided in thereceiving body (12) and having an outlet opening (22) spaced from thedrilling head (16; 46); a mixing member (31; 61) displaceably supportedin the inner tube (21), the drilling head (16; 46) having a receptacle(18; 48) adjacent to the mixing member (31; 61) for receiving a free end(32; 62) of the mixing member (21; 61) and a through-opening (17) forthe hardenable mass (26), and the receptacle (18; 48) of the drillinghead (16; 46) having a centering section (20; 50) that cooperates with acounter-centering section (33; 63) provided at the free end (32; 62) ofthe mixing member (31; 61) adjacent to the drilling head (16; 46).
 2. Arock anchor according to claim 1, wherein the centering section (20) ofthe receptacle (18) of the drilling head (16) has a funnel shape andtapers toward the free end of the drilling head (16).
 3. A rock anchoraccording to claim 1, wherein a wall section of the centering section(50) that surrounds the receptacle (48) of the drilling head (46) isformed concave.
 4. A rock anchor according to claim 1, wherein a wallsection of the counter-centering section (63) that surrounds the endregion of the free end of the mixing member (61) is formed convex.
 5. Arock anchor according to claim 1, wherein the centering section (20; 50)of the receptacle (18; 48) of the drilling head (16; 46) has a diameter(D1; D2) larger than a diameter (d1, d2) of the counter-centeringsection (33; 63) of the free end (32; 62) of the mixing member (31; 61).6. A rock anchor according to claim 1, wherein the counter-centeringsection (63) is formed of several centering elements (64) formed at thefree end (62) of the mixing member (61).
 7. A rock anchor according toclaim 6, wherein the centering elements (64) are arranged rotationallysymmetrically with respect to a longitudinal axis (23) of the inner tube(21).
 8. A rock anchor according to claim 1, further comprising a stop(19; 49) for the mixing member (31; 61) provide din the receptacle (18;48) of the drilling head (16; 46).